CVE-2021-4278 is a high-severity (CVSS 7.8) CWE-1321 vulnerability in tree-kit. A fix is available for tree-kit — see the affected versions and patch details below.
tree-kit vulnerable to Prototype Pollution
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2021-4278 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 378,567 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.
tree-kitnpmDescription
A vulnerability classified as problematic has been found in cronvel tree-kit up to 0.6.x. This affects an unknown part. The manipulation leads to improperly controlled modification of object prototype attributes ('prototype pollution'). Upgrading to version 0.7.0 is able to address this issue. The name of the patch is a63f559c50d70e8cb2eaae670dec25d1dbc4afcd. It is recommended to upgrade the affected component. The identifier VDB-216765 was assigned to this vulnerability.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | tree-kit | all versions | 0.7.0npm install tree-kit@0.7.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for tree-kit, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update tree-kit to 0.7.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-4278 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2021-4278 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2021-4278. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2021-4278 in your dependencies?
O3 Security finds CVE-2021-4278 across npm dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.